tools/python: Python 3 compatibility

convert-legacy-stream is only used for incomming migration from pre Xen 4.7,
and verify-stream-v2 appears to only be used by me during migration
development - it is little surprise that they missed the main converstion
effort in Xen 4.13.

Fix it all up.

Move open_file_or_fd() into a new util.py to avoid duplication, making it a
more generic wrapper around open() or fdopen().

In libxc.py, drop all long() conversion.  Python 2 will DTRT with int => long
promotion, even on 32bit builds.

In convert-legacy-stream, don't pass empty strings to write_record().  Join on
the empty argl will do the right thing.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

tools/python/scripts/verify-stream-v2

@@ -3,12 +3,15 @@
 
 """ Verify a v2 format migration stream """
 
+from __future__ import print_function
+
 import sys
 import struct
 import os, os.path
 import syslog
 import traceback
 
+from xen.util import open_file_or_fd as open_file_or_fd
 from xen.migration.verify import StreamError, RecordError
 from xen.migration.libxc import VerifyLibxc
 from xen.migration.libxl import VerifyLibxl
@@ -25,7 +28,7 @@ def info(msg):
             for line in msg.split("\n"):
                 syslog.syslog(syslog.LOG_INFO, line)
         else:
-            print msg
+            print(msg)
 
 def err(msg):
     """Error message, routed to appropriate destination"""
@@ -33,7 +36,7 @@ def err(msg):
         if log_to_syslog:
             for line in msg.split("\n"):
                 syslog.syslog(syslog.LOG_ERR, line)
-        print >> sys.stderr, msg
+        print(msg, file = sys.stderr)
 
 def stream_read(_ = None):
     """Read from input"""
@@ -56,7 +59,7 @@ def skip_xl_header():
     """Skip over an xl header in the stream"""
 
     hdr = rdexact(32)
-    if hdr != "Xen saved domain, xl format\n \0 \r":
+    if hdr != b"Xen saved domain, xl format\n \0 \r":
         raise StreamError("No xl header")
 
     _, mflags, _, optlen = unpack_exact("=IIII")
@@ -86,7 +89,7 @@ def read_stream(fmt):
         err(traceback.format_exc())
         return 1
 
-    except StandardError:
+    except Exception:
         err("Script Error:")
         err(traceback.format_exc())
         err("Please fix me")
@@ -94,35 +97,6 @@ def read_stream(fmt):
 
     return 0
 
-def open_file_or_fd(val, mode, buffering):
-    """
-    If 'val' looks like a decimal integer, open it as an fd.  If not, try to
-    open it as a regular file.
-    """
-
-    fd = -1
-    try:
-        # Does it look like an integer?
-        try:
-            fd = int(val, 10)
-        except ValueError:
-            pass
-
-        # Try to open it...
-        if fd != -1:
-            return os.fdopen(fd, mode, buffering)
-        else:
-            return open(val, mode, buffering)
-
-    except StandardError, e:
-        if fd != -1:
-            err("Unable to open fd %d: %s: %s" %
-                (fd, e.__class__.__name__, e))
-        else:
-            err("Unable to open file '%s': %s: %s" %
-                (val, e.__class__.__name__, e))
-
-    raise SystemExit(2)
 
 def main():
     """ main """
@@ -168,7 +142,7 @@ def main():
 if __name__ == "__main__":
     try:
         sys.exit(main())
-    except SystemExit, e:
+    except SystemExit as e:
         sys.exit(e.code)
     except KeyboardInterrupt:
         sys.exit(2)